leetcode 105 construct binary tree from preorder and inorder traversal

import utils.TreeNode;

import java.util.Arrays;

public class  {
  public TreeNode buildTree(int[] preorder, int[] inorder) {
    return helper(preorder, inorder, 0, preorder.length, 0, inorder.length);
  }
  public TreeNode helper(int[] preorder, int[] inorder, int prel, int prer, int inl ,int inr) {
    if (inl == inr) return new TreeNode(inorder[inl]);
    TreeNode root = new TreeNode(preorder[prel]);
    int i = inl;
    for (i = inl; i<inr; i++) {
      if (inorder[i] == root.val) {
        break;
      }
    }
    root.left = helper(preorder, inorder, prel+1,prel+(i-inl), inl, i-1);
    root.right = helper(preorder, inorder, prel+(i-inl)+1, prer, i+1, inr);
    return root;
  }
}